Secure Sketch Metamorphosis: Tight Unified Bounds.
Jeroen Delvaux, Dawu Gu, Ingrid M.R. Verbauwhede, Matthias Hiller, Meng-Day Yu · Lirias · 2015
A noisy non-uniformly distributed secret often needs to be transformed into a stable high-entropy key.Biometric systems and physically unclonable functions (PUFs) exemplify the need for this conversion.Secure sketches are a useful tool hereby as they alleviate the noisiness while keeping the corresponding min-entropy loss to a minimum.The novelty of our work is twofold.First, seven secure sketch constructions, all based on a binary [n, k, d] block code, are proven to be largely interchangeable.Despite having different looks and properties, all exhibit the same min-entropy loss, when fed with the same probability distribution.Second, for PUF-induced distributions with practical relevance, we derive new unified bounds on the min-entropy loss, considerably tighter than the more general well-known (n -k) bound.Our bounds allow for an efficient evaluation and are hence suitable for reducing the implementation footprint of the sketch.This is beneficial for resource-constrained devices in particular.